Automatic circuit breaker with contact arm ball joint



Sept 1, 1964 G. J. GlEssNER ETAL AUTOMATIC CIRCUIT BREAKER WITH CONTACT ARM BALL JOINT Filed Dec.

2 //H/ 5 x www E 9 5 4 4 M INVENTORJ Septl, 1964 G. J. GlEssNER ETAL AUTOMATIC CIRCUIT BREAKER WITH CONTACT ARM BALL JOINT 3 Sheets-Sheet 2 Filed Dec.

INVENTORS' QEORQE J.

SePt- 1, 1964 G. J. GlEssNER ETAL 3,147,352

AUTOMATIC CIRCUIT BREAKER WITH CONTACT ARM BALL JOINT I5 Sheets-Sheet 3 Filed Deo.

INVENTORS E u. @Er/YES@ United States Patent O 3,147,352 AUTOMATEC CIRCUIT BREAKER WITH CNTACT ARM BALL JOINT George J. Giessner, Oaklyn, NJ., and Martin V.

Zuhaty, Philadelphia, Pa., assignors to I-T-E Circuit Breaker Company, Philadelphia, Pa., a corporation of Pennsylvania Filed Dec. 23, 1969, Ser. No. 77,974

15 Claims. (tCl. 20G-116) The instant invention relates to circuit breaker mechanisms housed within a narrow molded casing and more particularly to a novel means for assuring the maintenance of an electrical conducting path between the contact arm and releasable cradle during operation of the circuit breaker.

In recent years it has been the practice to construct circuit breakers for home and light industrial applications with casings whose widths are one inch or multiples thereof. More recently, the trend has been to supply individual circuit breaker protection to many circuits even those carrying light loads. Because of this, the capacity of existing panelboards, while sufficient electrically, were not suicient in physical size to accommodate the greater numbers of circuit breakers. Further, panelboards having the requisite physical size to accommodate the greater number of circuit breakers were wasteful of material and space.

Thus, it became necessary to construct circuit breakers having narrow housings. For example, a typical circuit breaker of 20 amp rating was usually provided with a molded casing having a one inch width. A circuit breaker of this rating can be replaced by a circuit breaker whose molded insulating housing is one-half inch in width.

In the circuit breaker of this type described in the I. H. Leonard copending application Serial Number 11,768, tiled February 29, 1960, entitled Circuit Breaker Having Bimetal Rigidly Secured to Cradle, and assigned t the assignee of the instant invention, a latch means is provided which is comprised of main and intermediate latch members with the intermediate latch member having one portion thereof utilized as a latch surface for magnetic tripping and another portion utilized as a latch surface for the thermal tripping. The bimetal, or thermal tripping element, is positioned to deflect out of the plane of movement of the releasable cradle to which the bimetal is aixed while the latch members are arranged to pivot around axes perpendicular to the releasable cradle.

Until automatic tripping has actually occurred the relationship between the bimetal and intermediate latch member is unaffected by the position of the main latch member which is movable directly through the action of the magnetic tripping device. Similarly, a deflection of the bimetal Will in no way aiect the relationship between the elements comprising the magnetic trip means.

The absolute independence of the thermal and magnetic trip device results in the advantage of being able to adjust the trip characteristics of the breaker so as to achieve low magnetic tripping without utilizing a coil. Further, the thermal tripping characteristic may be calibrated prior to installing the thermal trip unit into the circuit breaker case. The latter is accomplished by providing a sub-assembly comprising a releasable cradle, the bimetal having one end rigidly secured to the cradle and the intermediate latch member pivoted to the cradle and operatively positioned so as to cooperate with the free end of the bimetal to form the latch for the thermal tripping means.

In the circuit breaker of the aforesaid copending application Serial No. 11,768, a portion of the series current path between the line and load terminals includes merely a pressure joint formed by the abutment of the contact arm against the releasable cradle. It has been found that ICC during circuit breaker operation the contact arm and cradle often separate drawing electric current arcs therebetween which causes the joint region to present a high resistance, so that objectionable local overheating occurs. The instant invention overcomes this diiiiculty by providing conducting paths which parallel the joint at the abutment between the contact arm and cradle.

The parallel conducting paths are formed by the U- shaped portion of a spring element which encompasses the joint region so as to sandwich the contact arm therebetween. The width of the contact arm is such that when it is placed between the arms of the U-shaped portion these arms are spread apart so that they become selfbiased into engagement with the Contact arm. The spring element is mounted to the cradle in such a manner as to be self-biased thereagainst. Even when the contact arm and cradle separate the spring element provides a good electrical conducting path between the contact arm and cradle.

The spring element also includes another portion which engages the pivot pin for the intermediate latch member, thereby retaining the latch member and pivot pin mounted to the cradle. At the same time the spring element provides biasing means which urges the intermediate latch member axially along its pivot pin toward the cradle. This assures a uniform latch bite for successive timedelayed tripping operations.

The utilization of the spring element materially simplies assembly in that no deforming tools are required to mount the spring element, the intermediate latch member, and its pivot pin to the cradle. In addition, the U- shaped portion of the spring element provides guidance for the Contact arm as it moves between the circuit open and closed positions, thereby eliminating the need for the welded member utilized in the device of the aforesaid copending application 11,768.

Time delayed tripping is also made more precise by providing the end of the bimetal with a rolled-over portion. The intermediate latch member is in operative engagement with the rolled-over portion so that frictional forces acting between the bimetal and intermediate latch are substantially less than they would be were a flat surface engaged by the intermediate latch as in prior art devices.

Accordingly, a primary object of this invention is to provide a narrow molded case circuit breaker which is economical to construct, is reliable in operation, and is simple to calibrate.

Another object is to provide a circuit breaker in which the contact arm and releasable cradle yare biased together to form a butt joint and .to include novel means which provides parallel conducting paths bypassing the butt joint.

Still another object is to provide a circuit breaker of this type which utilizes a single spring element to provide guidance for .the contact arm, provide conducting paths between the contact arm vand releasable cradle, secure a latch member to the cradle, and bias the latch member to a predetermined position relative tok the cradle.

A further object is to provide a circuit breaker of this type in which the portions of the contact arm engaged by the spring element are shaped as spherical segments so as to reduce frictional forces.

A still further object is to provide a circuit breaker of this type in which the bimetal element is provided with a rolled-over por-tion which is engaged by a latch member for maintaining the releasable cradle in reset position.

These as well as other objects of this invention shall become readily apparent after reading the following description of the accompanying drawings in which:

FIGURES 1-3 are side elevations of a circuit breaker constructed in accordance with the teachings of the instant invent-ion, with the cover of the casing removed to reveal the operating mechanism. In FIGURE 1 the circuit breaker is in the On position, in FIGURE 2 the circuit breaker is in the manual Off position, and in FIGURE 3 the circuit breaker is in the Tripped position.

FIGURE 1A is a fragmentary cross-section of the circuit breaker housing taken through line 1A1A o-f FIG- URE 1 looking in the direction of arrows 1A-1A.

FIGURE 4 is an exploded perspective of the circuit breaker operating mechanism.

FIGURE 5 is a side elevation of the cradle sub-as- -sembly.

FIGURES 5A and 5B are cross-sections taken through lines SA-SA and 5B-5B, respectively, of FIGURE 5, looking in thev direction of the respective arrows.

FIGURE 6 is an end view of the contact arm.

FIGURE 7 is a fragmentary side elevation of the cradle in the region of the joint between the contact arm and the cradle.

FIGURES 8 and 9 are fragmentary side elevations showing the relationship between the cont-act arm and cradle in the joint region. In FIGURE 8 the contact arm is in normal operating position, while in FIGURE 9 the contact arm has been moved to the position it occupies relative to the cradle when contact welds are present during automatic tripping.

Now referring to the figures, circuit breaker 20 includes a housing comprised of a case 21 and cover 22 mated to each other laiong line 23 and secured by rivets 23a. The current path through circuit breaker 20 comprises line terminal 24, conducting strap 25, stationary contact 26, movable contact 27, contact arm 28, the pressure joint 29 at the upper end of contact 28, releasable cradle 30, bimetal 31, conducting braid 32, load terminal member 33, and load terminal 79.

Adapter means 77, of a type fully described in the I H. I eonard copending application Serial No. 18,411, led March 29, 1960, entitled Panelboard Adapter, and assigned to the Iassignee of the Iinstant invention is utilized to electrically connect line terminal 24 to a panelboard bus bar (not shown).

Circuit breaker 20 includes an operating member 34 having an extension 35 which extends upwardly through an opening 36 in the top of housing 21, 22 to provide a manual operating handle. Operating member 34 is also provided with an arcuate portion 37 extending in the direction of movement of handle 35 and disposed within arc groove 38 of case 21 and a similar groove in cover 22. The upper end of handle arm 39 extends into suitable recesses of operating member 34 while the lower end of arm 39 abuts against a rounded internal formation of case 21 to form a pivot 40 for operating member 34.

Main operating spring 41 is secured at one end thereof 42 to arm 39 where the upper end thereof engages member 34 while the other end 43 of spring 41 is connected to movable contact arm 28. Spring 41 is a tension. spring comprised of an open loop with elongated arms extending in opposite directions. The tension force exerted by spring 41 urges the upper end of contact arrn 28 to abut cradle 30 at joint 29.

With sub-assembly 100 (FIGURE 5) in the latched position of FIGURES 1 and 2, circuit breaker 20 may be operated manually between the On and Off positions. When handle 35 is moved to the right with respect to FIGURE 1 at such time as the spring end at 42 passes to the right of a line joining spring end 43 and joint 29, the line of action of spring 41 will be so positioned as to affect a snap opening of contacts 26, 27 by pivoting contact arm 28 in .a counterclockwise direction -about joint 29 to the Oif position of FIGURE 2. The reverse action takes place as handle 35 is moved to the left with respect to FIGURE 2. During this operation, at such time as the line of action of spring 41 extending between spring ends 42, 43 passes to the left of the line joining spring end 43 and joint 29 in FIGURE 2, contact arm 28 will be snapped in a clockwise direction about joint 29 to the closed position of FIGURE 1.

Sub-assembly 100 (FIGURE 5) comprises cradle 30 which is a generally V-shaped member having an opening 44 near the apex thereof which receives a case embossment 45 serving as a pivot for sub-assembly 100. Bimetal 31, which forms a part of sub-assembly 100, is iixedly secured at one end 46 thereof as by welding to cradle leg 47 in the region of aperture 44. Sub-assembly 100 further comprises intermediate latch member 48 pivotally mounted at pin 49 to the offset portion 30a at the free end of cradle leg 4t). In forming portion 30a stop formation 71 is also formed. Stop 71 cooperates with the notch 72 in latch member 48 to limit movement of latch member 48 about its pivot pin 49. Pin 49 is constructed of insulating material as is sheet 70 which is interposed between latch member 48 and cradle offset portion 30a. Thus, latch member 48 is insulated from cradle 30.

Pin 49 and latch member 48 are secured to cradle 30 by element which is constructed of a good electrically conductive spring material. Element 94) is an elongated member having a U-shaped portion 91 at one end and at the other end an olfset portion 92 with an open ended slot 93.

The arm 94 of U-shaped portion 91, which is not directly connected to the main portion 95 of element 90. confronts one surface of main portion 95 while portion 92 is offset beyond the other surface of main portion 95. The web of U-shaped portion 91 is disposed within cradle notch 96 with the upper end of contact arm 28 being positioned between the arms of the U-shaped portion 91 which encompass the region of joint 29 to provide guidance for arm 28 as it moves between the positions of FIGURES 1-3. The arms of U-shaped portion 91 are slightly spread as a result of engagement with embossments 97A, 97B (FIGURE 6) extending from opposite surfaces of contact arm for a purpose to be hereinafter explained.

The portion of element 90 defining slot 93 is received by annular groove 98 in the body of pivot pin 49 to retain pin 49 mounted to cradle 30. As slot 93 is mated to pin 49 the main portion 95 snaps over cradle projection 88 to retain element 90 mounted to cradle 30. Thus, it is seen that elements 30, 48, 49, 70 and 90 are readily assembled without the necessity of utilizing special deforming tools or assembly jigs.

Offset portion 30a must be bent from its free position in order for slot 93 to receive the reduced portion of pin 49. In so being bent, the main portion 95 is firmly seated against cradle 30 and intermediate latch 48 is biased axially along pin 49 toward cradle offset portion 30a. This assures a uniform latch bite for successive resettings after thermal tripping. The rounded portion 99 at the end of pin 49 opposite its enlarged head 89 serves to align subassembly 100 with respect to the internal walls of housing Since contact arm 28 abuts cradle 30 at joint 29 to the right of embossment 45, the force exerted by main operating spring 41 acts to rotate sub-assembly 100 counterclockwise about pivot 45. However, sub-assembly 100 is restrained against movement in a counterclockwise direction through the engagement of intermediate latch member 48 with main latch member 51. Main latch member S1 is comprised of spring material and includes a portion of reduced area which extends over the back of magnet 52 so as to form a pivot at 53 for armature 54 which is secured to main latch member 51 by welding.

Magnet 52 is of generally U-shaped cross-section with terminal member 33 passing between the arms of the U to form the energizing turn therefor. The biasing action of the spring material forming main latch member S1 urges armature 54 in a clockwise direction about its pivot 53 away from magnet 52. The lower end of armature 54 abuts a case formation 56 to establish the air gap between armature 54 and magnet 52 and also establishes the latching position for member 51. Magnetic tripping takes place when a predetermined magnitude of current flows through terminal member 33 causing magnet 52 to generate ux which attracts armature 54 eounterclockwise about pivot 53. This moves main latch member 51 with respect to FIGURE l so that sub-assembly 100 is no longer restrained. Thus, sub-assembly 100v under the influence of main operating spring 41 rotates in a counterclockwise direction about pivot 4S. When pivot 29 moves to the left of the line of action of spring 41 in its position of FIGURE 1, spring 41 will urge contact arm 28 in a counterclockwise direction about pivot 29 to bring about a snap opening of contacts 26, 27.

The circuit breaker elements are now in the tripped position of FIGURE 3 with sub-assembly 100 being positioned by the abutment of case embossment 55 and cradle surface 55a while one side of contact arm offset 75 abuts cover formation 76. Offset 75 extends at right angles to the plane of movement of contact arm 28 and movable contact 27 is mounted to the other side of offset 75.

After magnetic tripping, resetting is accomplished by moving operating handle 35 to the extreme right position from the intermediate tripped position of FIGURE 3. During this movement handle arm extension 60 engages cradle 30 along surface 61 so that sub-assembly 100 is moved clockwise against the force of spring 41 to the latched position of FIGURE 2. As latch member 48 moves past latch member 51 the rounded portion 63 of intermediate latch member 48 cams latch 51 to the right until latch surface 64 passes below the lower end of main latch member 51.

Time delay tripping is accomplished by a deflection of the free end of bimetal 31 out of the plane of movement of cradle 30. When this deflection is sufficient to free bimetal offset tip 31a from intermediate latch 48 the action of tension spring 41 will rotate cradle 30 in a counterclockwise direction about pivot 45. Initially intermediate latch member 48 is retained by main latch member 51 so that there is relative movement between cradle 30 and intermediate latch member 48 about pivot 49. As the distance between pivot 49 and main latch member 51 increases, a point is reached Where intermediate latch member 48 is free of main latch member 51 and the subassembly 100 moves freely to the tripped position of FIGURE 3. It is to be noted that bimetal tip 31a presents a rolled surface for engagement by latch member 48 so that shear forces are materially reduced and successive trip operations are more uniform.

Resetting after thermal tripping is accomplished by moving handle 35 from the intermediate trip position of FIGURE 3 to the extreme right position of FIGURE 2. At the latter portion of this movement intermediate latch member 48 engages case embossment 65 which forces intermediate latch member 48 in a counterclockwise direction about its pivot 49 to a point where member 48 is free of the edge of bimetal extension 31a and at this time the free end of bimetal 31 moves toward the plane of movement of cradle 30 into latching position.

It is to be noted that as the latch bite between bimetal offset 31a and member 48 changes due to a deection of bimetal 31 the latch bite between surface 64 and member 51 is not affected. Similarly, a change in the magnetic latch bite 64, 51 in no way affects the thermal latch bite 31a, 48. Thus, the thermal and magnetic trips are operated independently of one another.

Cover 22 is mated with case 21 to form housing chamber 80, wherein the operating mechanism is disposed, also forms vent opening 81 (FIGURE 6) which extends for distance X (FIGURE l) along the bottom of housing 21, 22. Vent 81 is greatly elongated, being Very narrow in width, say .020. It is to be noted that the cover surface 82 forming vent 81 extends toward vent 81 initially experiencing turbulence within chamber 81 since vent 81 is so narrow. After the gases are substantially deionized the upper portion of surface 82 not confronted by surface 83 acts to direct the deionized gases through vent 81 out of housing 21, 22.

During movement of contact arm 28 the upper end thereof often loses direct contact with cradle 30 at pressure joint 29. If there were no parallel conducting paths, arcing would occur at joint 29 which would soon become pitted and thereafter present a high resistance connection. The instant invention provides these parallel conducting paths in the form of spring element whose body portion is self biased against cradle leg 50 and Whose U- shaped portion arms are self biased into engagement with contact arm 28 at embossments 97A, 97B. The engagement between element 90 and embossments 97A, 97B is maintained even though contact arm 28 moves a considerable distance away from joint 29.

Embossments 97A, 97B are formed as spherical segments to reduce the frictional forces between spring element 90 and contact arm 28 which must be overcome in moving contact arm relative to cradle 30.

In circuit breakers of the type hereinbefore described it is not unusual for the contacts 26, 27 to weld with spring 41 not being of sufficient strength to break these welds. For manual breaking of contact welds handle extension 39 in pivoting clockwise, as handle 35 is moved to the right from its position of FIGURE 1, and engages offset 101 which is depressed from the plane of contact arm 28 (FIG- URE 4). Thus, the manual opening force is applied directly to contact arm 28 for breaking of contact welds.

The breaking of contact welds during automatic tripping is facilitated by the unique shapes of cradle 30 and contact arm 28 at the region of joint 29. This is best explained by reference to FIGURES 7-9.

The legs 47, 50 of cradle 30 are arranged to form notch 102 which receives contact arm 28. Notch 102 is of generally V-shape, as indicated by the dotted line in FIGURE 7, and is provided at its apex region with an offset reentrant portion 103. The upper end of contact arm 28, at the upper end thereof, is provided with a section of reduced width having a rounded portion 104 which is normally entered into reentrant portion 103 of notch 102 as in FIGURE 8. It is to be noted that rounded portion 104 appears to be comprised of an arc greater than a semi-circle.

During automatic tripping when cradle 30 is first unlatched the forces of main spring 41 acting on contact arm merely tend to move contact 27 in the plane of its engagement with contact 26 so that only a shearing force is present to separate contact welds. As cradle 30-pivots counterclockwise contact arm rounded portion 104 appears to be moved out of reentrant notch portion 102 to the position of FIGURE 9 and is engaged by cradle surface 105 in the apex region of notch 102.

Surface 105 is so inclined that spring 41 in rotating cradle 30 now exerts a component of force upon contact arm 28 urging contact arm rounded portion 104 back into notch reentrant portion 103. This force component produces a bending moment which acts to pry contacts 26, 27 apart and is of sufficient magnitude to break welds at contacts 26, 27.

Thus, the invention provides a single spring element which is self-locking to the cradle and provides guidance for the contact arm, provides a conducting path between the contact arm and cradle, secures the intermediate latch to the cradle, and biases this latch to its operative position relative to the cradle. This materially simplifies assembly and produces a more rugged reliable device.

Although there has been described preferred embodiments of this invention, many variations and modifications will now be evident to those skilled in the art and, therefore, the scope of this invention is to be limited not by the specific disclosure herein detailed, but only by the appended claims.

We claim:

1. A-circuit breaker comprising a pair of cooperating contacts and an operating mechanism for operating said contacts into and out of engagement; said mechanism including a releasable cradle, latch means for restraining said cradle in a reset position, an operating spring urging said cradle to a tripped position, and a manually operable member for operating said contacts into and out of engagement; said mechanism further including a tripping means having a portion operatively positioned for engagement with said latch means and when deflected sufficiently to disengage said latch means permitting said spring to move said cradle to its said trip position wherein said contacts are disengaged; a movable contact arm; one end of said movable contact arm carrying one of said cooperating contacts; the other end of said movable contact arm abutting said cradle to form a pivotal connection therewith; said pivotal connection comprising part'of a series current path, including said cooperating contacts, through said circuit breaker; the operation of said operating mechanism effecting separating movement apart of said cradle and contact arm at said pivotal connection, to defeat said abutting relationship therebetween; conducting means in direct engagement with said cradle and said contact arm about the lextent of said separating movement apart for providing current carrying path means which parallels said pivotal connection.

2. A circuit breaker comprising a pair of cooperating contacts and an operating mechanism for operating said contacts into and out of engagement; said mechanism including a releasable cradle, latch means for restraining said cradle in a reset position, an operating spring urging said cradle to a tripped position, and a manually operable member for operating said contacts into and out of engagement; said mechanism further including a tripping means having a portion operatively positioned for engagement with said latch means and when deflected sufficiently to disengage said latch means permitting said spring to move said cradle to its said trip position Wherein said contacts are disengaged; a movable contact arm;

Vone end of said movable contact arm carrying one of said cooperating contacts; the other end of said movable contact arm being mounted to said cradle at a pivotal connection; said pivotal connection comprising part of a series currentl path, including said cooperating contacts, through said circuit breaker; conducting means in direct engagement with said cradle and said contact arm providing current carrying path means which parallels said pivotal connection; said conducting means comprising an element of spring material; said element being self-locked to said cradle and Vself-biased into engagement with said cradle and said contact arm.

3. A circuit breaker comprising a pair of cooperating contacts and an operating mechanism for operating said contacts into and out of engagement; said mechanism including a releasable cradle, latch means for restraining said cradle in a reset position, an operating spring urging said cradle to a tripped position, and a manually operable member for operating said contacts into and out of engagement; said mechanism further including a tripping means having a portion operatively positioned for engagement with said latch means and when deflected sufficiently to disengage said latch means permitting said spring to move said cradle to its said trip position Wherein said contacts are disengaged; a movable contact arm; one end of said movable contact arm carrying one of said cooperating contacts; the other end of said movable contact arm being mounted to said cradle at a pivotal connection; said pivotal connection comprising part of a series current path, including said cooperating contacts, through said circuit breaker; conducting means in direct engagement with said cradle and said contact arm providing current carrying path means which parallels said pivotal connection; said latch means comprising a member pivotally mounted to said cradle at a first axis; said conducting means comprising an element having a first portion maintaining said member mounted to said cradle; said element being comprised of spring material; said first portion providing means biasing said member along said axis to a predetermined position relative to said cradle.

4. A circuit breaker comprising a pair of cooperating contacts and an operating mechanism for operatingsaid contacts into and out of engagement; said mechanism including a releasable cradle, latch means for restraining said cradle in a reset position, an operating spring urging said cradle to a tripped position, and a manually operable member for operating said contacts into and out of engagement; said mechanism further including a tripping means having a portion operatively positioned for engagement With said latch means and when deilected sufficiently to disengage said latch means permitting said spring to move said cradle to its said trip position Wherein said contacts are disengaged; a movable contact arm; one end of said movable contact arm carrying one of said cooperating contacts; the other end of said movable contact arm being mounted to said cradle at a pivotal connection; said pivotal connection comprising part of a series current path, including said cooperating contacts, through said circuit breaker; conducting means in direct engagement with said cradle and said contact arm providing current carrying path means which parallels said pivotal connection; said latch means comprising a member pivotally mounted to said cradle at a rst axis; said conducting means comprising an element having a first portion maintaining said member mounted to said cradle; said element being comprised of spring material; said first portion providing means biasing said member along said axis to a predetermined position relative to said cradle; said element being self-locked to said cradle and self-biased into engagement with said cradle and said contact arm.

5. A circuit breaker comprising a pair of cooperating contacts and an operating mechanism for operating said contacts into and out of engagement; said mechanism including a releasable cradle, latch means for restraining said cradle in a reset position, an operating spring urging said cradle to a tripped position, and a manually operable member for operating said contacts into and out of engagement; said mechanism further including a tripping means having a portion operatively positioned for engagement With said latch means and when deflected sufficiently to disengage said latch means permitting said spring to move said cradle to its said trip position Wherein said contacts are disengaged; a movable contact arm; one end of said movable contact arm carrying one of said cooperating contacts; the other end of said movable contact arm being mounted to said cradle at a pivotal connection; said pivotal connection comprising part of a series current path, including said cooperating contacts, through said circuit breaker; conducting means in operative engagement with said cradle and said contact arm providing current carrying paths which parallel said pivotal connection; said pivotal connection being formed at a region Where said contact arm other end abuts said cradle being urged thereagainst by said spring; said conducting means comprising an element of spring material mounted to said cradle and having a U-shaped portion encompassing said region to form a guidance means for said contact arm as said contacts are engaged and disengaged.

6. The circuit breaker as set forth in claim 5 in which said contact arm other end is provided With projections extending from opposite surfaces of said contact arm and engaged by the arms of the U-shaped portion.

7. The circuit breaker as set forth in claim 6 in which the projections are spherical segments.

8. The circuit breaker as set forth in claim 5 in which the element is self-locked to saidy cradle and is self-biased into engagement with said cradle and said contact arm.

9. The circuit breaker as set forth in claim 8 in Which the latch means comprises a member pivotally mounted to said cradle at a first axis; said element having a first portion maintaining said member mounted to said cradle.

10. The circuit breaker as set forth in claim 9 in which the first axis comprises a pin having a reduced portion; said element first portion having an open ended slot into which said pin reduced portion is disposed.

11. The circuit breaker as set forth in claim l in which said element biases the member along the first axis to a predetermined position relative to the cradle.

12. The circuit breaker as set forth in claim 11 in which the element includes a main portion interposed between said U-shaped portion and said first portion; said first portion offset to one side of the plane of said main portion; one arm of said U-shaped portion being disposed in a plane parallel to the plane of said main portion to the other side thereof.

13. A circuit breaker comprising a pair of cooperating contacts and an operating mechanism for operating said contacts into and out of engagement; said mechanism including a releasable cradle, latch means for restraining said cradle in a reset position, an operating spring urging said cradle to a tripped position, and a manually operable member for operating said contacts into and out of engagement; said mechanism further including a tripping means having a portion operatively positioned for engagement with said latch means and when deflected sufficiently to disengage said latch means permitting said spring to move said cradle to its said trip position wherein said contacts are disengaged; a movable contact arm; one end of said movable contact arm carrying one of said cooperating contacts; the other end of said movable contact arm being mounted to said cradle at a pivotal connection; said pivotal connection comprising part of a series current path, including said cooperating contacts, through said circuit breaker; conducting means in direct engagement with said cradle and said contact arm providing current carrying path means which parallels said pivotal connection; said conducting means comprising an element of spring material.

14. A circuit breaker comprising a pair of cooperating contacts and an operating mechanism for operating said contacts into and out of engagement; said mechanism including a releasable cradle, latch means for restraining said cradle in a reset position, an operating spring urging said cradle to a tripped position, and a manually operable member for operating said contacts into and out of engagement; said mechanism further including a tripping means having a portion operatively positioned for engagement with said latch means and when defiected sufiiciently to disengage said latch means permitting said spring to move said cradle to its said trip position Wherein said contacts are disengaged; a movable contact arm; one end of said movable contact arrn carrying one of said cooperating contacts; the other end of said movable contact arm being mounted to said cradle at a pivotal connection; said pivotal connection comprising part of a series current path, including said cooperating contacts, through said circuit breaker; conducting means in direct engagement with said cradle and said contact arm providing current carrying path means which parallels said pivotal connection; said latch means comprising a member pivotally mounted to said cradle at a rst axis; said conducting means comprising an element having a first portion maintaining said member mounted to said cradle.

15. A circuit breaker comprising a pair of cooperating contacts and an operating mechanism for operating said contacts into and out of engagement; said mechanism including a releasable cradle, latch means for restraining said cradle in a reset position, an operating spring urging said cradle to a tripped position, and a manually operable member for operating said contacts into and out of engagement; said mechanism further including a tripping means having a portion operatively positioned for engagement With said latch means and when deilected sufficiently to disengage said latch means permitting said spring to move said cradle to its said trip position Wherein said contacts are disengaged; a movable contact arm; one end of said movable contact arm carrying one of said cooperating contacts; the other end of said movable contact arm being mounted to said cradle at a pivotal connection; said pivotal connection comprising part of a series current path, including said cooperating contacts, through said circuit breaker; conducting means in direct engagement with said cradle and said contact arm providing current carrying path means which parallels said pivotal connection; said latch means comprising a member pivotally mounted to said cradle at a first axis; Said first axis being defined by an insulating pin; an insulating sheet interposed between said member and said cradle thereby electrically insulating said member from said cradle.

References Cited in the file of this patent UNITED STATES PATENTS 2,320,437 Jennings June 1, 1943 2,653,202 Cole Sept. 22, 1953 2,758,174 Cole Aug. 7, 1956 2,844,689 Middendorf July 22, 1958 OTHER REFERENCES Thumim: Quick-Acting Release Latches, Mechanical Engineering, November 1939, pages 807-811 relied upon. 

1. A CIRCUIT BREAKER COMPRISING A PAIR OF COOPERATING CONTACTS AND AN OPERATING MECHANISM FOR OPERATING SAID CONTACTS INTO AND OUT OF ENGAGEMENT; SAID MECHANISM INCLUDING A RELEASABLE CRADLE, LATCH MEANS FOR RESTRAINING SAID CRADLE IN A RESET POSITION, AN OPERATING SPRING URGING SAID CRADLE TO A TRIPPED POSITION, AND A MANUALLY OPERABLE MEMBER FOR OPERATING SAID CONTACTS INTO AND OUT OF ENGAGEMENT; SAID MECHANISM FURTHER INCLUDING A TRIPPING MEANS HAVING A PORTION OPERATIVELY POSITIONED FOR ENGAGEMENT WITH SAID LATCH MEANS AND WHEN DEFLECTED SUFFICIENTLY TO DISENGAGE SAID LATCH MEANS PERMITTING SAID SPRING TO MOVE SAID CRADLE TO ITS SAID TRIP POSITION WHEREIN SAID CONTACTS ARE DISENGAGED; A MOVABLE CONTACT ARM; ONE END OF SAID MOVABLE CONTACT ARM CARRYING ONE OF SAID COOPERATING CONTACTS; THE OTHER END OF SAID MOVABLE CONTACT ARM ABUTTING SAID CRADLE TO FORM A PIVOTAL CONNECTION THEREWITH; SAID PIVOTAL CONNECTION COMPRISING PART OF A SERIES CURRENT PATH, INCLUDING SAID COOPERATING CONTACTS, THROUGH SAID CIRCUIT BREAKER; THE OPERATION OF SAID OPERATING MECHANISM EFFECTING SEPARATING MOVEMENT APART OF SAID CRADLE AND CONTACT ARM AT SAID PIVOTAL CONNECTION, TO DEFEAT SAID ABUTTING RELATIONSHIP THEREBETWEEN; CONDUCTING MEANS IN DIRECT ENGAGEMENT WITH SAID CRADLE AND SAID CONTACT ARM ABOUT THE EXTENT OF SAID SEPARATING MOVEMENT APART FOR PROVIDING CURRENT CARRYING PATH MEANS WHICH PARALLELS SAID PIVOTAL CONNECTION. 